Dermal, types

In a double-blind study of photodamaged skin, it has been demonstrated that papillary dermal type Icollagen formation was reduced by 56% in photodamaged skin compared with... 

Epidermal type - increased melanin in the basal, suprabasal, and stratum comeum layers [19,68,123, 126,127] dermal melanophages present [19,47], Dermal type- melanin increase in the superficial and deep dermis melanin-laden macrophages and mel-anosomes within the superficial dermis and perivas-cularly in the middermis [19,68,123,126,127]. Mixed type - both the epidermal and dermal melanin are increased [19, 68,126,127],... 

Although this histopathological classification of melasma is widely accepted [45], Kang et al. s study suggested that there may not be a true dermal type since the melanophages in the demtis of this type of melasma may actually be undiagnosed acquired bilateral nevus of Ota-like macules (ABNOM) or Hori s macules [77]. 

In order to determine the dermal exposure of volunteers to chlorpyrifos, the penetration of chlorpyrifos through the outer whole-body dosimeter (coveralls) to the inner body dosimeter (t-shirt and briefs) was measured. The penetration factor was calculated for each volunteer in the study from the experimental data by dividing the amount of chlorpyrifos on the t-shirt and brief sample by the amount of chlorpyrifos on the torso section of the coveralls. This method of calculation assumes that the surface area of the torso section of the coveralls is nearly the same as the surface area of the t-shirt and briefs worn directly under the torso section of the coveralls. A mean penetration factor for each worker type was calculated by averaging all the worker volunteer... 

Through the early 1980s, dermal exposure to the body (except hands) was measured via some type of patch that varied in size and composition. In early studies, patches were placed only on exposed parts of the body... 

It has been demonstrated in other cell types that lutein can inhibit expression of MMPs and/ or activity (Philips et al., 2007). For example, in dermal fibroblasts lutein inhibits expression of MMP-1 and decreases levels of MMP-2 protein (Philips et al., 2007). In melanoma cells, lutein inhibits MMP-1 expression while stimulating TIMP-2 (Philips et al., 2007). Moreover it has been shown that lutein inhibits elastin expression in fibroblasts subjected to oxidative stress by exposure to ultraviolet light (Philips et al., 2007). These results clearly indicate that lutein can play an important role in remodeling of the extracellular matrix. 

Only a few in vivo dermal toxicity studies have been reported so far. Huczko and Lange [50] evaluated the potential of raw CNTs to induce skin irritation by conducting two routine dermatological tests (patch test on 40 volunteers with allergy susceptibilities and Draize rabbit eye test on four albino rabbits). Koyama etal. [51] showed the biological responses to four different types of carbon nanotubes (SWNTs, two types of MWNTs with different diameters, and cup-stacked carbon nanotubes) after their subcutaneous implantation in mice. Both tests [50, 51] showed no or poor irritation effects. However, the in vitro studies in epidermal cell lines exposed to CNTs, and also a more recent report on the toxic outcomes of topical exposure of mice to SWNTs [46], have raised concerns over these assessments. Clearly, this is an area requiring further scientific evaluation. 

Acute-Duration Exposure. Information is available regarding the effects of acute-duration inhalation exposure of humans to acrylonitrile and the effects are characteristic of cyanide-type toxicity. Quantitative data are limited but are sufficient to derive an acute inhalation MRL. Further studies of humans exposed to low levels of acrylonitrile in the workplace would increase the confidence of the acute MRL. Studies in animals support and confirm these findings. No studies are available on the effects of acute-duration oral exposure in humans however, exposure to acrylonitrile reveals neurological disturbances characteristic of cyanide-type toxicity and lethal effects in rats and mice. Rats also develop birth defects. Animal data are sufficient to derive an acute oral MRL. Additional studies employing other species and various dose levels would be useful in confirming target tissues and determining thresholds for these effects. In humans, acrylonitrile causes irritation of the skin and eyes. No data are available on acute dermal exposures in animals. 

Although vesicants do not produce the same type of dermal damage in animals as they do in humans, they are still susceptible to the cytotoxic and systemic toxicities of these agents. 

Route of administration may account for wide variations in the toxic action of fenvalerate. Most authorities agree that fenvalerate is most toxic to rodents when administered by intercere-broventricular injection relative to other routes — indicating the importance of the brain in the Type II poisoning syndrome. Fenvalerate was decreasingly toxic when administered intravenously, intraperitoneally, orally, and dermally (Lawrence and Casida 1982 Flannigan et al. 1985 Grissom etal. 1985 Bradbury and Coats 1989a Williamson etal. 1989). 

Exposure to arsenic has been associated with different types of human cancers such as respiratory cancers and epidermoid carcinomas of the skin, as well as precancerous dermal keratosis. The epidemiological evidence of human carcinogenicity is supported by carcinogenesis in experimental animals (Deknudt et al. 1986). 

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